Grip force control for robotic surgical instrument end effector

ABSTRACT

Methods of controlling a gripping force of an end effector of a robotically-controlled surgical instrument are provided. The method includes receiving a first input signal indicative of a high grip level input at a master gripping mechanism that controls a slave gripping force of the end effector; receiving a second input signal indicative of a user&#39;s readiness to operate the surgical instrument to perform a surgical procedure; and outputting an actuation signal in response to receiving the first input signal and the second input signal together to increase the slave gripping force from a first level to a second level higher than the first level during the surgical procedure.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority of U.S. ProvisionalApplication No. 61/550,356 (filed Oct. 21, 2011; entitled “GRIP FORCECONTROL FOR ROBOTIC SURGICAL INSTRUMENT END EFFECTOR”).

TECHNICAL FIELD

The present disclosure is generally directed to controlling a surgicalinstrument end effector. More particularly, aspects of the presentdisclosure relate to controlling the gripping force of an end effectorfor a robotically-controlled surgical instrument.

INTRODUCTION

Minimally invasive surgical techniques generally attempt to performsurgical procedures while minimizing damage to healthy tissue.Robotically-controlled surgical instruments can be used to performvarious minimally invasive surgical procedures remotely. In suchsystems, surgeons manipulate various input devices at a surgeon console(sometimes referred to herein as master inputs). The input at thesurgeon console is communicated to a patient side cart that interfaceswith one or more robotically-controlled surgical instruments, whereteleoperated/telerobotic manipulation of the surgical instrument occursto perform a surgical and/or other procedure on the patient.

Minimally invasive, robotically-controlled surgical instruments may beused in a variety of operations and have various configurations. Manysuch instruments include a surgical end effector mounted at a distal endof a long shaft that is configured to be inserted (e.g.,laporoscopically or thoracoscopically) through an opening (e.g., bodywall incision, natural orifice) to reach a remote surgical site within apatient. In some instruments, an articulating wrist mechanism is mountedto the distal end of the instrument's shaft to support the end effectorand alter an orientation (e.g., pitch and/or yaw) of the end effectorwith reference to the shaft's longitudinal axis.

Telerobotically controlled end effectors may be configured to performvarious functions, including any of a variety of surgical proceduresthat are conventionally performed in either open or manual minimallyinvasive surgical procedures. Examples include, but are not limited to,sealing, cutting, cauterizing, ablating, suturing, stapling, etc. Theend effectors may include a gripping device, such as jaws or blades, incases in which tissue may need to be grasped and held as a procedure isperformed, for example, during sealing (e.g., via cauterizing) orcutting of the tissue. In some instances, the control of the grippingdevice of a surgical instrument end effector occurs through master gripinput from a surgeon at the surgeon console. To control motion of an endeffector, servo-actuators (e.g., servo motors), can be used to transmitforce or torque to various components that ultimately transmit from atransmission mechanism that interfaces with the patient side manipulatordown the shaft and to the end effector.

In some cases, when using a surgical instrument that includes an endeffector having a gripping device, it may be desirable to use thegripping device to move tissue and/or other material at the surgicalsite by gripping the same with the gripping device. When using agripping device in such a manner, it may be desirable to use lessgripping force in comparison to a gripping force that may be desired toachieve another surgical procedure, such as, for example, sealing and/orcutting. For example, lower gripping forces may be desirable when usingthe gripping device to move tissue and/or other body parts/materialsaround so as to minimize the risk of damaging the same. On the otherhand, higher gripping forces may be desirable when using the grippingdevice for other procedures. For example, if the gripping force is nothigh enough during a procedure such as cutting, a translating blade usedto cut transversely through the tissue could push the tissue distallyinstead of cutting all the way through the tissue. Likewise, if thegripping force is not high enough during a procedure such as sealing(e.g., cauterizing), for example, effective contact for sealing oftissue surfaces (e.g., opposing wall portions of a vessel) may not beachieved.

The user may indicate that a higher gripping force is to be used by, forexample, squeezing a gripping input mechanism that controls the grippingforce at the end effector. The user may inadvertently squeeze thegripping input mechanism too hard, resulting in a higher gripping forceat the end effector during operations of the end effector in which ahigher gripping force is not desired. For example, prior to or afterperforming a procedure that requires a higher gripping force, such assealing or cutting, the user may squeeze the gripping input mechanismhard enough to result in higher gripping forces at the end effector.Using higher gripping forces during operations that do not requirehigher gripping forces, such as while the user is manipulating tissueprior to or after performing a sealing or cutting procedure, can lead toundesirable and/or unintentional movements. For example, undesired pitchor yaw motions may occur as the end effector rolls. In addition,unintentional and/or unsteady movement of the end effector may occurduring the high grip force action due to movement in one of pitch/yaw bya wrist, roll of the shaft, and/or translation along the shaft. Suchmovement instability of the end effector can negatively impact thedesired surgical procedure.

There exists a need, therefore, to provide gripping force control of asurgical instrument end effector gripping device in order to address thevarious issues faced when performing robotically-controlled surgicalprocedures that rely on relatively high gripping forces by such an endeffector.

SUMMARY

The present disclosure solves one or more of the above-mentionedproblems and/or demonstrates one or more of the above-mentioneddesirable features. Other features and/or advantages may become apparentfrom the description that follows.

In accordance with at least one exemplary embodiment, the presentteachings contemplate a method of controlling a gripping force of an endeffector of a robotically-controlled surgical instrument. The methodincludes receiving a first input signal indicative of a high grip levelinput at a master gripping mechanism that controls a slave grippingforce of the end effector; receiving a second input signal indicative ofa user's readiness to operate the surgical instrument to perform asurgical procedure; and outputting an actuation signal in response toreceiving the first input signal and the second input signal together toincrease the slave gripping force from a first level to a second levelhigher than the first level during the surgical procedure.

Additional objects and advantages will be set forth in part in thedescription which follows, and in part will be obvious from thedescription, or may be learned by practice of the present disclosureand/or claims. At least some of these objects and advantages may berealized and attained by the elements and combinations particularlypointed out in the appended claims.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not restrictive of the invention, as disclosed or claimed. Theclaims should be entitled to their full breadth of scope, includingequivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure can be understood from the following detaileddescription either alone or together with the accompanying drawings. Thedrawings are included to provide a further understanding of the presentdisclosure, and are incorporated in and constitute a part of thisspecification. The drawings, which are incorporated in and constitute apart of this specification, illustrate one or more embodiments of thepresent disclosure and, together with the description, serve to explaincertain principles and operation. In the drawings,

FIG. 1A is a state diagram depicting a gripping force control scheme fora robotically-controlled surgical instrument in accordance with at leastone exemplary embodiment;

FIG. 1B is a state diagram depicting a gripping force control scheme fora robotically-controlled surgical instrument in accordance with anotherexemplary embodiment;

FIG. 2 is a state diagram depicting a gripping force control scheme fora robotically-controlled surgical instrument in accordance with at leastone exemplary embodiment;

FIG. 3 is a state diagram depicting a gripping force control scheme fora robotically-controlled surgical instrument in accordance with at leastone exemplary embodiment;

FIG. 4 is a state diagram depicting a gripping force control scheme fora robotically-controlled surgical instrument in accordance with at leastone exemplary embodiment;

FIG. 5 is a state diagram depicting a gripping force control scheme forrobotically-controlled surgical instrument in accordance with at leastone exemplary embodiment;

FIG. 6 is a perspective view of a robotically-controlled surgicalinstrument in accordance with at least one exemplary embodiment;

FIG. 7 is a detailed view of an exemplary end effector corresponding toa portion of the surgical instrument of FIG. 6 in accordance with anexemplary embodiment;

FIG. 8 is a diagrammatic view of an exemplary robotic surgical systemconfigured to operate a robotically-controlled surgical instrument inaccordance with at least one exemplary embodiment;

FIG. 9A is a side view of a master grip input mechanism in an openposition in accordance with an exemplary embodiment; and

FIG. 9B is a side view of a master grip input mechanism in a closedposition in accordance with an exemplary embodiment.

DETAILED DESCRIPTION

This description and the accompanying drawings illustrate exemplaryembodiments and should not be taken as limiting, with the claimsdefining the scope of the present disclosure, including equivalents.Various mechanical, compositional, structural, electrical, andoperational changes may be made without departing from the scope of thisdescription and the invention as claimed, including equivalents. In someinstances, well-known structures, and techniques have not been shown ordescribed in detail so as not to obscure the disclosure. Like numbers intwo or more figures represent the same or similar elements. Furthermore,elements and their associated aspects that are described in detail withreference to one embodiment may, whenever practical, be included inother embodiments in which they are not specifically shown or described.For example, if an element is described in detail with reference to oneembodiment and is not described with reference to a second embodiment,the element may nevertheless be claimed as included in the secondembodiment. Moreover, the depictions herein are for illustrativepurposes only and do not necessarily reflect the actual shape, size, ordimensions of the system or the electrosurgical instrument.

It is noted that, as used in this specification and the appended claims,the singular forms “a,” “an,” and “the,” and any singular use of anyword, include plural referents unless expressly and unequivocallylimited to one referent. As used herein, the term “include” and itsgrammatical variants are intended to be non-limiting, such thatrecitation of items in a list is not to the exclusion of other likeitems that can be substituted or added to the listed items.

In accordance with various exemplary embodiments, the present disclosurecontemplates controlling a robotically-controlled surgical instrumentend effector gripping device such that a relatively lower or highergripping force may be exerted by the gripping device, depending upon theapplication involved as indicated by input received at a surgeonconsole. For example, for procedures such as grasping and moving tissueand/or other material (e.g., body structures) at a surgical site, theend effector gripping device may be controlled to exert a relativelylower gripping force to allow the tissue to be grasped and moved withoutunnecessarily damaging the tissue. On the other hand, for proceduressuch as, for example, sealing or cutting, the end effector grippingdevice may be controlled to exert a higher gripping force sufficient tohold the tissue relatively firmly to effectively perform the desiredsurgical procedure that is implemented with a relatively high grippingforce. Various exemplary embodiments, therefore, provide an automaticcontrol technique of an end effector gripping device to elevate and holdthe gripping force at relatively higher levels during the appropriateprocedures and lower levels during other procedures in which the highgripping force is not necessary and may not be desirable.

In addition, in order to avoid instability of the surgical instrumentend effector due to the higher gripping force that occur when the usergrips a master gripping input mechanism beyond a gripping forcethreshold, various exemplary embodiments limit the higher gripping forcefrom occurring when the operation that necessitates the higher grippingforce is not being performed. In particular, in accordance with variousexemplary embodiments, in order to constrain the higher gripping forceonly to the procedure that requires the higher gripping force, a methodof controlling a gripping force of an end effector provides a highergripping force based on two inputs from a surgeon—the first input beingindicative of a higher gripping level input by the user at a surgeonmaster gripping input and the second input being indicative of theuser's readiness to operate the surgical instrument to perform asurgical procedure that utilizes the relatively higher gripping force ofthe end effector. In accordance with various exemplary embodiments, thegripping force of the end effector (slave grip force) is controlled byaltering or limiting a torque of an electric motor (e.g., servo motor)at the patient side cart that interfaces with a drive input of atransmission mechanism associated with the surgical instrument.

In addition, various exemplary embodiments provide a method of locking(i.e., preventing actuation) one or more degrees of freedom of the endeffector during certain surgical procedures to provide a higher level ofstability while the procedure is being performed.

Although the exemplary embodiments and description below focus mainly oncontrolling gripping force of a surgical instrument during sealing andcutting procedures, the principles of the exemplary embodiments could beapplied to other surgical procedures, including but not limited to, forexample, clamping of a vessel or other hollow body structure, cuttingtissue using pivoting blades of an end effector, surgically staplingtissue, and/or other procedures where a relatively high gripping forcemay be desirable. For some of these instruments and associatedprocedures, the relatively high end effector gripping force is generatedby a servo motor torque that is higher than the highest motor torquenormally used to operate other jawed instruments, such as surgicalshears, tissue graspers, needle drivers, and the like.

With reference to FIG. 6, an exemplary embodiment of arobotically-controlled surgical instrument 600 is depicted. FIG. 6 is aperspective view of the surgical instrument 600, and FIG. 7 is adetailed view of an exemplary, non-limiting embodiment of thecorresponding portions denoted in FIG. 6 that the surgical instrument600 can include. The directions “proximal” and “distal” are used hereinto define the directions as shown in FIG. 6, with distal generally beingin a direction further along a kinematic arm or closest to the surgicalwork site in the intended operational use of the instrument 600, forexample, in use for performing surgical procedures. The “proximal” and“distal” directions as used herein are labeled on FIG. 6. As shown inFIG. 6, the instrument 600 generally includes a force/torque drivetransmission mechanism 602 at its proximal end, an instrument shaft 604mounted to the transmission mechanism 602, and an end effector 606disposed at the distal end of the shaft 604. In the exemplary embodimentshown in FIG. 6, the surgical instrument 600, a portion of which isshown in more detail in FIG. 7, also includes an optional articulatingwrist mechanism 608 mounted at the distal end of the shaft 604 tosupport the end effector 606 and change its orientation with referenceto the shaft's 604 longitudinal axis.

In an exemplary embodiment, the instrument 600 is configured to bemounted on and used with a minimally invasive robotic surgical system,which in an exemplary embodiment includes a patient side cart 800, asurgeon console 802, and an electronics/control console 804, asillustrated in a diagrammatic view of FIG. 8 (it is noted that thesystem components in FIG. 8 are not shown in any particular positioningand can be arranged as desired, with the patient side cart beingdisposed relative to the patient so as to effect surgery on thepatient). A non-limiting, exemplary embodiment of a robotic surgicalsystem with which the instrument 600 can be utilized is a da Vinci® Si(model no. IS3000) commercialized by Intuitive Surgical, Inc. ofSunnyvale, Calif.

The robotic surgical system is used to perform minimally invasiverobotic surgery by interfacing with and controlling a variety ofsurgical instruments, as those of ordinary skill in the art aregenerally familiar. The patient side cart 800 includes various arms 810for holding, positioning, and manipulating various tools. As shown inFIG. 8, one arm 810 is configured to interface with and control arobotically-controlled surgical instrument 600, including an endeffector 606. In general, the surgeon console 802 receives inputs from asurgeon by various input devices, including but not limited to, gripinput levers 900 a, 900 b of a master grip input mechanism 806 and footpedals 808, etc., and serves as a master controller by which the patientside cart 800 acts as a slave to implement the desired motions of thesurgical instrument(s) (e.g., instrument 600) interfaced therewith, andaccordingly perform the desired surgical procedure. The patient sidecart 800 can include a plurality of jointed arms 810 configured to holdvarious tools, including, but not limited to, for example, a surgicalinstrument with an end effector (e.g., surgical instrument 600), and anendoscope (not shown). An electronic data processing system, including aprocessing device, and which may be provided at one or more of thesurgeon console 802, the electronics/control console 804 and the patientside cart 800, may receive and process inputs from the surgeon console802 and control the manipulation of the surgical instrument 600 at thepatient side cart 800 based on the inputs received at the surgeonconsole 802. However, the present disclosure is not limited to receivinginputs at the surgeon console 802, and inputs may be received at anydevice which results in manipulation of an end effector of the surgicalinstrument 600. The surgical instrument 600 may be manipulated at thepatient side cart 800, or alternatively, may be manipulated incombination with any other type of surgical instrument support device,or entirely separately from a support device, as a result of inputsreceived from the user, e.g., the surgeon.

In various exemplary embodiments, inputs from the surgeon console 802 orfrom input units otherwise accessible to a surgeon can be provided tothe controller(s) via various master input devices, such as, forexample, one or more pedals 808, and one or more hand-held grip inputlevers 900 a, 900 b. In various exemplary embodiments described herein,the pedals 808 may be used to send signals to perform a sealing and/orcutting operation of the robotically controlled surgical instrument 600and the hand-held grip input levers 900 a, 900 b may be used to sendsignals to control movement of the wrist 608 (e.g., pitch/yaw movement),the instrument shaft 604 (e.g., roll and/or translation), and/or openingand closing (gripping) movement of an end effector gripping device(e.g., jaws or blades). Those having ordinary skill in the art arefamiliar with the general use of such teleoperated robotic surgicalsystems to provide input from a surgeon at a surgeon console toultimately effect operation of a surgical instrument interfacing with apatient side cart.

Based on the master inputs at the surgeon console 802, the patient sidecart 800 can interface with the transmission mechanism 602 of thesurgical instrument 600 to position and actuate the instrument 600 toperform a desired medical procedure. For example, based on the masterinputs from the surgeon console 802, the transmission mechanism 602,which includes various torque/drive input mechanisms (e.g., in the formof drive disks) configured to be driven via teleoperated servo actuators(e.g., motors) associated with the patient side cart 800, can transmitthe inputs into various forces and/or torques to ultimately actuate(drive) the overall instrument 600 to perform a surgical procedure. Forexample, master inputs from the surgeon console 802 can be converted atthe patient side cart 800 through the transmission mechanism 602 to rollshaft 604, articulate the wrist 608 relative to the shaft (e.g., inpitch and/or yaw), and/or to open and close the gripping device 700 (seeFIG. 7).

The electronics/control console 804, which may include, for example, anelectrosurgical processing unit, receives and transmits various controlsignals to and from the patient side cart 800 and the surgeon console802, and can transmit light and process images (e.g., from an endoscopeat the patient side cart 800) for display, such as, for example, display812 at the surgeon console 802 and/or on a display 814 associated withthe electronics/control console 804. Those having ordinary skill in theart are generally familiar with such electronics/control consoles ofrobotically controlled surgical systems.

The patient side cart 800 is positioned proximate to a patient and thesurgical instrument 600 is used to perform various surgical proceduresat a work site in the patient's body through the use of the remotelyactuated end effector 606. Exemplary surgical procedures that the endeffector 606 can perform include, but are not limited to, for example,clamping of a vessel or other hollow body structure, cutting tissueusing pivoting blades of an end effector, and/or other procedures wherea relatively high gripping force may be desirable.

With reference now to FIG. 7, an exemplary embodiment of an end effector606 of the instrument 600 is shown, although the end effector 606 is notlimited thereto and may be any end effector configured for use toperform surgical procedures that utilize gripping forces. The endeffector 606 may be provided with a gripping device 700, such as, forexample, opposing jaws 701 a, 701 b or gripping blades (e.g., similar toscissors), provided at the end effector 606. The jaws 701 a, 701 b areconfigured to move to and from an open position and a closed position.In the closed position, the jaws 701 a, 701 b can grip material, such astissue and the like. In an exemplary embodiment, the jaws 701 a, 701 bcan deliver electrosurgical energy, for example via electrodes providedon opposing faces of the jaws 701 a, 701 b, sufficient to seal (e.g.,cauterize) tissue together. In addition, the end effector 606 may alsoinclude a cutting element in the form of a short cutting blade 702attached to a cable 704. The cutting blade 702 may be received in agroove 706 of the bottom jaw 701 b and operable to traverse in proximaland distal directions along a length of the jaws 701 a, 701 b to performa cutting operation. While FIG. 7 shows an example of an end effectorthat may be used during operation of the gripping force control method,it is to be understood by those of ordinary skill in the art that anytype of end effector may be used in which a relatively high grippingforce is used during the implementation of a surgical procedure, suchas, for example, cutting or sealing. For more details regarding anexemplary embodiment of a surgical instrument and end effector withwhich gripping force control according to the present disclosure may beimplemented, reference is made to U.S. Provisional Patent ApplicationNo. 61/491,698 (filed on May 31, 2011; entitled surgical instrument withmotor), the entire contents of which are incorporated herein byreference.

With reference now to FIGS. 1A-1B, and 2-4, event-based state diagramsare shown which illustrate exemplary methods of controlling the grippingforce of the end effector 606 of the surgical instrument 600. The statediagrams illustrate elements S0-Sn (where n=1, 2, 3, . . . ). ElementsS0-Sn illustrate the occurrence of events and are not necessarilyintended to correspond with periods of time. Elements S0-Sn do notnecessarily correspond to the same occurrences in each of the statediagrams and are to be read independently of one another, depending onthe individual state diagram. However, one of ordinary skill in the artwould understand that elements S0-Sn may relate to times at which eachof the events occurs. At S0, prior to the user, e.g., a surgeon,exerting actuating force on master grip input levers 900 a, 900 b of amaster grip input mechanism 806 at the surgeon console 802, the mastergrip input signal 100 is in an “off” state. Also, the gripping force(e.g., slave grip 102) of the gripping device 701 is in an “off” stateat S0. As described above, in an exemplary embodiment, therefore notorque is provided by the teleoperated servo motor that controls theopening/closing (gripping) of the jaws 701 a, 701 b. Further, aprocedure input 104 indicative of the user's command to cause a surgicalprocedure relying on a relatively high gripping force (e.g., sealing orcutting) to be performed at the end effector 606 of the surgicalinstrument 600 is not received, and thus the seal or cut procedure input104 is indicated to be in an off state in the state diagram of FIG. 1A.

When the user at the surgeon console 802 is ready to perform a procedureusing the gripping device 700, e.g., jaws 701 a, 701 b, at S1 the usermanipulates a master grip input mechanism 806 at the surgeon console802. For example, the surgeon may squeeze grip levers 900 a, 900 btogether. However, the master grip input is not limited thereto and maybe an input other than squeezing the gripping levers 900 a, 900 btogether that provides an indication from a user, e.g., a surgeon, thatthe user desires a high slave gripping force at the end effector. In anexemplary embodiment, for example, the master grip input may be a userpressing one or more of the pedals 808.

In various exemplary embodiments, as depicted in the diagrammatic viewof FIGS. 9A and 9B, a so-called “bumper” mechanism may be used toincrease the resistance against squeezing the levers 900 a, 900 btogether that the user experiences as two grip levers 900 a, 900 b arebrought closer together. As shown in FIGS. 9A and 9B, as the grip levers900 a, 900 b are brought into closer contact, a biasing transitionmechanism including, for example, a first biasing mechanism, such as,for example, a first coiled spring 902 (shown in FIGS. 9A-9B), a magnet,etc., and a second biasing mechanism, such as, for example, a secondcoiled spring 904, a magnet, etc. provides haptic feedback to the userto provide an indication of squeezing against a first level ofresistance. Compression of the first biasing mechanism 902 may indicatea lower gripping input range, while compression of the second biasingmechanism 904 may indicate a higher gripping input range. In anexemplary embodiment, the second biasing mechanism, for example, secondcoiled spring 904 (see FIGS. 9A-9B) may have a greater stiffness thanthe first biasing mechanism, e.g., first spring 902. In an alternativeexemplary embodiment, the biasing system may rely on a single variablerate spring where portions of the variable rate spring correspond to thefirst biasing mechanism and the second biasing mechanism, rather thanthe two different springs shown in FIGS. 9A and 9B. For examples ofbiasing mechanisms, reference is made to U.S. Pat. No. 6,594,552 (issuedJul. 15, 2003; entitled “GRIP STRENGTH WITH TACTILE FEEDBACK FOR ROBOTICSURGERY”), the entire contents of which are incorporated by referenceherein.

The biasing transition mechanism can provide the user with feedback thatthe gripping device of the end effector is transitioning from arelatively lower gripping force to a relatively higher gripping force.When the master grip input 100 is initiated at S1, and a master gripinput signal is generated, the torque of the motor that ultimatelycontrols the gripping force (slave grip 102) of the correspondinggripping device 700, such as jaws 701 a, 701 b, begins to increase toprovide a gripping force to the gripping device 700. In anotherembodiment, the motor may actuate a clutch mechanism, which actuates thegripping of the end effector. As the master grip input signal 100increases between S1 to S2, the corresponding force of the slave grip102 increases from zero gripping force at S1 to a low gripping force atS2.

At S2, the master grip input signal 100 reaches a squeezing forcethreshold that corresponds to a predetermined, high grip level at themaster grip input mechanism 806. In various exemplary embodiments, thesqueezing force threshold may correspond to any input at the mastergrip, such as, for example, actuating the grip levers 900 a, 900 b ofthe master grip input mechanism 806 beyond some threshold level ofactuation, e.g., beyond a threshold range of motion of the grip levers900 a, 900 b toward one another, that may indicate that a higher slavegripping force is desired at the end effector 606. In another exemplaryembodiment, when a mechanism is used to provide haptic feedback to theuser, such as in FIGS. 9A-9B, the compression amount may correspond to acompression amount into a higher gripping force input range, forexample, approximately 80% compression applied to the second biasingmechanism or 80% compression applied to the portion of the variable ratespring corresponding to a second biasing mechanism. That is, theactuation threshold may be indicated by, for example, the compression ofthe second biasing mechanism, such as second spring 904, to a point thatis indicative of the user's intent to apply the higher gripping, ratherthan a repositioning or shifting of the user's grip. For example, acompression of the second biasing mechanism to a point 80% to 100% ofthe fully closed/actuated position, may be indicative of an intentionalcompression by the user. It should be understood that the actuationthreshold range is exemplary, and a specific range may be chosen basedon the type of procedure, the type of grip used, the type of biasingmechanism used, and other factors.

One of ordinary skill in the art would recognize that the presentdisclosure is not limited to the biasing mechanisms described and any ofa variety of biasing devices or gripping level indicators may be used.Regardless of the configuration of the biasing mechanism, when themaster grip input mechanism 806 includes biasing mechanisms, the mastergrip input mechanism 806, such as gripping levers 900 a, 900 b, providesfeedback to the user to indicate a lower gripping input level and ahigher gripping input level. In addition, as above, the systemrecognizes that a higher gripping input level is achieved when thesqueezing force threshold at the master grip input mechanism 806 isreached, and at this point, the master grip input signal 100 is at arelatively high gripping input level.

Setting the squeezing force threshold to correspond to a relatively highamount of the compression of the second biasing mechanism can help toensure that the user is intending to provide a higher level of grip ofthe master grip input mechanism 806, e.g., by providing feedback to theuser. This can provide an additional safety feature to assist inpreventing the user from increasing the master gripping force, andconsequently the slave gripping force, to too high a level when the useris not intending for that level to be used.

As shown in FIG. 1A, in response to the user actuating the master gripinput mechanism 806 (e.g., grip levers), according to some embodiments,the motor torque (and consequently slave grip force 102) also increases,thereby increasing the gripping force of the gripping device, indicatedby zero slave gripping force at 51 increased to a low gripping force atS2. In other embodiments, the motor actuates a clutch mechanism at theforce/torque drive transmission mechanism 602, which causes the slavegripping force. At S2, a relatively low slave gripping force is output.In various exemplary embodiments, the relatively low end effector gripactuation torque output at S2 may be, for example, about 0.3 Nm.

From S0 through S2, the procedure input 104, e.g., a sealing, cutting orstapling procedure, is not received and the procedure input is in an offstate. At S3, an input indicative of a user's desire for the endeffector 606 to perform a surgical procedure that relies on a relativelyhigh gripping force is received, indicated in the state diagram asprocedure input 104 transitioning from an off state to an on state. Thesurgical procedure to be performed may be one or more of, for example, asealing procedure, a cutting procedure, etc. However, it is to beunderstood that these procedures are merely meant to be exemplary andany other type of procedure that would be implemented using a highgripping force by an end effector gripping device may be indicated byactuation of the input devices, such as pedals 808.

At S3, when both the master grip input signal 100 has reached thesqueezing force threshold level and an additional input has beenreceived at a procedure input device, such as one or more pedals 808, atthe surgeon console 802, indicating that the high gripping forceprocedure is to be performed, i.e., the procedure input 104 is in an onstate, then the motor torque and corresponding slave gripping force 102is increased from the relatively low levels shown between S2 and S3, tothe relatively higher levels depicted at S3. In various exemplaryembodiments, the high torque level of the servomotor that ultimatelycauses actuation of end effector grip, which results in the relativelyhigher gripping force, may be about 1.5 Nm. The relatively high torquelevel of the motor and the relatively high gripping force of the endeffector gripping device 700 are maintained at least through to thecompletion of the procedure, such as, e.g., a sealing procedure, acutting procedure, etc. It is noted that the 0.3 Nm lower gripping forceat the end effector and the 1.5 Nm higher gripping force at the endeffector may be altered, depending on a desired slave gripping force. Inanother embodiment, the servomotor may actuate a clutch mechanismprovided at the force/torque drive transmission mechanism 602, whichactuates the end effector, increasing the gripping force at the endeffector to the higher gripping force.

In some exemplary embodiments, a grip force torque control mechanism maybe interfaced with the servomotor to ultimately control the delivery ofthe torque forces to actuate the end effector.

Reference is made to U.S. Provisional Application No. 61/491,804 (filedMay 31, 2011; entitled “GRIP FORCE CONTROL IN A ROBOTIC SURGICALINSTRUMENT”), the entire contents of which are incorporated herein byreference, for an exemplary embodiment of a vessel sealing and cuttinginstrument that utilizes a spring assembly in the transmission backendto transmit and control the torque from the servomotor that is deliveredto the end effector. Those having ordinary skill in the art wouldappreciate that the control techniques described herein could be used incombination with such a transmission system.

The surgical procedure, such as sealing or cutting, may occur while boththe additional input, such as the depression of one or more pedals 808,is actuated and the squeezing force at the master grip input levers 900a, 900 b is maintained at or above the squeezing force threshold. At S4,the system senses the completion of the desired procedure and signalssuch to the user at the surgeon console 802, or at any location thatwould provide such an indication to a user, after which the user may beprompted to stop the master grip input by, for example, releasing thegrip levers 900 a, 900 b. The surgical procedure, such as sealing,cutting or stapling, therefore ends at S4, indicated by the off state inthe state diagram. The surgical procedure may be indicated by endingactuation of the seal, cut or staple input device (e.g., releasing oneof the pedals 808), by recognizing, for example, that the tissue hasbeen cut or by recognizing that the tissue has been sealed (e.g., byanalyzing the conductance of the tissue), etc.

The surgical procedure may end when the user, e.g., the surgeon,releases the additional input device, such as, for example, one or morepedals 808. In another embodiment, the surgical procedure is performeduntil a processing device, such as an electrosurgical processing unitat, for example, the electronics/control console 804, senses that theprocedure has been completed based on detecting information from thetissue. For example, the procedure may be sensed to have been completedwhen the tissue is determined to be less conductive after, for example,a sealing procedure. In another example, a cutting element position maybe used to indicate that the procedure, such as a cutting procedure, iscomplete. One of ordinary skill in the art would recognize that theprocedure may be performed only while the input device is actuated ormay be performed upon actuation of the input device and ended after aprocessing device determines that the procedure may end, such as, forexample, when the gripped tissue has been fully cut, after a designatedamount of time has elapsed from the initiation of the surgicalprocedure, etc.

In the exemplary embodiment shown in FIG. 1A, the master grip inputsignal 100 is maintained in an on state after the surgical procedureends at S4. The master grip input signal 100 can be maintained in the onstate, for example, until a releasing threshold is sensed at the mastergrip levers 900 a, 900 b of the master grip input mechanism 806. Thereleasing threshold may be a releasing amount of release of the mastergrip levers 900 a, 900 b beyond a specific releasing amount and mayprovide a safety mechanism to ensure that a user is intending to stop aprocedure that uses a relatively high gripping force. The releasingthreshold may be approximately 20 percent or more of a releasing amountof the master grip levers 900 a, 900 b at the master grip inputmechanism 806. In an exemplary embodiment, the releasing threshold maybe about a 20% release of the second biasing mechanism of the mastergrip input mechanism 806 when the grip levers 900 a, 900 b have beenreleased at S5. That is, the releasing threshold may be indicated by,for example, the release of the second biasing mechanism, such as secondspring 904 shown in FIGS. 9A-9B, a bumper, etc., to a point that isindicative of the user's intent to release the grip, rather than arepositioning or shifting of the user's grip. For example, a release ofthe second biasing mechanism to a point 20% to 40% away from the fullyclosed/actuated position, may be indicative of an intentional release bythe user. It should be understood that the release range is exemplary,and a specific range may be chosen based on the type of procedure, thetype of grip used, the type of biasing mechanism used, and otherfactors. If the user, e.g., a surgeon, releases the master grip inputlevers 900 a, 900 b of the master grip input mechanism 806 at thesurgeon console 802, when a processing device recognizes that the griplevers 900 a, 900 b have been released beyond the releasing threshold atS5, the slave gripping force 102 decreases from the high torque levelindicative of a high grip at S5. The slave gripping force 102 maydecrease from the higher torque level to the lower torque level or, inan alternative embodiment, may decrease from the higher torque levelindicative of the high gripping force to no torque.

In an alternative embodiment, as shown in FIG. 1B, instead of remainingat the relatively high levels after the end of the surgical procedure atS4, the motor torque and corresponding slave gripping force 102 canautomatically drop to a relatively low level when the surgical procedureis complete, but prior to the releasing threshold being reached.

Although FIGS. 1A and 1B show a sealing or cutting operation, one ofordinary skill in the art would understand that a combined sealing andcutting operation may occur.

FIG. 2 is a state diagram of a method for controlling gripping force ofa robotically-controlled surgical instrument end effector that performsa sealing procedure followed by a cutting procedure in accordance withanother exemplary embodiment. FIG. 2 is similar to FIG. 1 at S0-S4 inrelation to the master grip input 100, the slave gripping force 102(which may be based on motor torque, for example), and the additionalseal input 200. According to this embodiment, however, after the sealingprocedure is performed at S3-S4, the motor torque and slave grippingforce 102 return to a relatively low torque level at S4 until asubsequent operation, such as an arming operation which corresponds to areadiness of the user to perform a cutting procedure, occurs at S5. Inan alternative embodiment, shown in FIG. 3, the slave gripping force 102remains at the relatively high torque level from S4 to S5.

In order to provide an additional safety feature to prevent a surgeonfrom unintentionally performing a cutting procedure until the surgeonintends for the procedure to occur, at S5, the user provides a secondadditional input 202, for example through actuation of an input device,such as one or more of pedals 808 (which may be a different pedal, forexample, than the pedal used for the additional seal input 200), toindicate a readiness to actuate the surgical instrument 600 to performthe cutting procedure, i.e., the surgical instrument is “armed”. The“arming” state is indicated in the state diagram as the arm/cut input202 transitioning from an off state at S4 to an on state at S5 inanticipation of a cutting procedure. When the arming input 202 has beenreceived at S5, if the motor torque and slave gripping force 102 are atrelatively low levels, as shown in FIG. 2, they increase to relativelyhigh levels at S5 during the “arming” operation. Following the arminginput by the user, an output signal can be output to provide feedback tothe user that indicates that the user has “armed” the surgicalinstrument 600.

In the alternative, if the motor torque and slave gripping force 102were not decreased between the sealing and arming stages at S3 and S5,respectively, then the relatively high levels can be maintained. Thehigh motor torque and corresponding slave gripping force 102 can bemaintained after the arming of the end effector 606 occurs at S5. Thearm/cut input 202 transitioning from an on state at S5 to an off stateat S6 in the state diagram indicates that the input to “arm” thesurgical instrument 600 has ended.

After “arming” the surgical instrument 600, a user at the secondadditional input device, e.g., one or more of the pedals 808 at thesurgeon console 802, provides another input to begin the cuttingprocedure at S7, which is indicated in the state diagram as the arm/cutinput 206 transitioning from the off state at S6 to the on state at S7.After the cutting procedure ends, indicated by the arm/cut input 202returning to an off state at S8, the motor torque may either bemaintained at the relatively high torque level until the releasingthreshold has been reached at S9, as shown in FIG. 2, or the motortorque may drop to the relatively low torque level or no torqueimmediately following the cutting operation.

For additional details regarding arming the surgical instrument prior toperforming the cutting operation, reference is made to U.S. ProvisionalPatent Application No. 61/491,647 (filed on May 31, 2011; entitled“POSITIVE CONTROL OF ROBOTIC SURGICAL INSTRUMENT END EFFECTOR”), theentire contents of which are incorporated herein by reference.

It may be understood that while the exemplary embodiment of FIG. 2indicates that the motor torque and slave gripping force 102 aremaintained at the relatively high torque level from the initiation ofthe arming input at S5 through the beginning of the cutting operation atS7, in an alternative embodiment, they may decrease from a high torquelevel to a low torque level between the end of the arming input at S6and the beginning of the cutting operation at S7. In another embodiment,the relatively low torque and slave gripping force levels can bemaintained from the end of the sealing operation at S4 through theinitiation of the cutting operation at S7. In yet another embodiment,the motor torque may be lowered to the low torque level after thesealing operation at S4, raised to the high torque level during thearming operation at S5, lowered to the low torque level after the end ofthe arming operation at S6 and then ultimately raised to the high torquelevel during the cutting operation at S7. It will be understand by thoseof ordinary skill in the art that any combination of torque and slavegripping force levels may be applied, with the exception of the sealingor cutting procedures which require the higher gripping force, and thushigher torque level, through the pendency of those procedures.

In addition, as shown in FIG. 3, the motor torque and slave grippingforce 102 may be maintained at the relatively high levels from theinitiation of the sealing operation at S3 through at least the end ofthe cutting operation at S8 and optionally until the releasing thresholdhas been achieved at S9.

As shown in FIG. 4, in an exemplary embodiment, the sealing proceduremay not be performed and only an arming and subsequent cutting proceduremay be performed. The slave gripping force 102, controlled by the motortorque for example, may be increased at the arming operation at S3 to arelatively high level and maintained at the high level either throughthe pendency of the cutting operation at S6 or until the releasingthreshold has been achieved at S7.

As mentioned above, in various exemplary embodiments, it may bedesirable to control DOF movement of the surgical instrument, e.g., ofthe wrist and/or shaft, when performing various surgical procedures.Such control may be desirable, for example, to provide stability and/orother control over the surgical instrument during procedures thatrequire high gripping force. Accordingly, various exemplary embodiments,contemplate locking and unlocking (i.e., allowing or preventing) one ormore DOF movement of the surgical instrument depending on the state ofthe surgical instrument and the particular procedure being performed bythe surgical instrument.

Turning now to FIG. 5, a state diagram that depicts an exemplary controlmethod, including control over the DOF movement of the surgicalinstrument, is depicted. The degrees of freedom (DOFs) of the surgicalinstrument, such as the pitch and yaw through the wrist mechanism 606,the roll through the shaft 604 and the movement of the instrument 600 inX, Y, and Z directions, which is controlled by the jointed arms 810 ofthe patient side cart 800, are locked or unlocked depending on, forexample, the operation involved. For purposes of simplicity, the slavegripping force 102 has been omitted as the unlocking and locking of theDOFs 500 occurs independently of the operation of the slave grippingforce 102.

At S3, when the sealing input is received and the master grip input isabove the gripping force threshold, the DOFs 500 are locked, indicatedby the transition from the off state at S2 to the on state at S3. Whenthe sealing procedure ends at S4, the DOFs 500 may be unlocked topermit, for example, the surgeon to be able to manipulate the surgicalinstrument to move tissue or the like. In an alternative embodiment, theDOFs 500 may be maintained in a locked state following the sealingprocedure at S4. Turning back to FIG. 5, when an input is received toindicate an armed state of the surgical instrument, at S5, if the DOFs500 have been unlocked, the DOFs 500 are locked during the armingoperation. The DOFs 500 may be locked through the end of arming at S6,through the initiation of cutting at S7, through the end of cutting atS8, and through until the releasing threshold has been achieved at S9.

In an alternative embodiment, the DOFs 500 may be unlocked from afterthe sealing procedure at S4 through the initiation of the cuttingprocedure at S7, whereupon the DOFs 500 are locked, i.e., the DOFs 500are unlocked during the arming procedure. In another alternativeembodiment, the DOFs 500 may be unlocked between each of the procedures,e.g., between S4 and S5, and between S6 and S7. Further, the DOFs 500may be unlocked immediately following the cutting procedure at S8.Additionally, one or more DOFs 500 may be selectively locked or unlockedbetween procedures, e.g., the sealing or cutting procedures, and/oroperations, e.g., the arming operation, or during the procedures oroperations.

While the unlocking and locking of the DOFs 500 occurs independently ofthe higher and lower slave gripping forces at the end effector, the DOFs500 are typically locked while the higher gripping force occurs at theend effector and the DOFs 500 are typically unlocked while the lowergripping force or the zero gripping force occurs at the end effector.

While procedures such as sealing and cutting have been disclosed, one ofordinary skill in the art would recognize that the present disclosure isnot limited to the sealing and cutting procedures described and any of avariety of procedures that utilize a surgical instrument, e.g.,stapling, etc. may be used.

Therefore, various exemplary embodiments in accordance with the presentdisclosure can provide a gripping force control scheme that increases agripping force of an end effector gripping device to a higher level whentwo inputs indicative of an increased grip level and an initiation of asurgical procedure are both received. Further, various exemplaryembodiments of the present disclosure also can enhance stability andcontrol of a surgical instrument during a surgical procedure, even whenrelatively high gripping forces are used, by locking and unlockingvarious instrument DOF motions depending on the operational state of thesurgical instrument.

The embodiments can be implemented in computing hardware (computingapparatus) and/or software, such as (in a non-limiting example) anycomputer that can store, retrieve, process and/or output data and/orcommunicate with other computers. The results produced can be displayedon a display of the computing hardware. One or more programs/softwarecomprising algorithms to effect the various responses and signalprocessing in accordance with various exemplary embodiments of thepresent disclosure can be implemented by a processor of or inconjunction with the electronics/control console 804, such as anelectrosurgical processing unit discussed above, and may be recorded oncomputer-readable media including computer-readable recording and/orstorage media. Examples of the computer-readable recording media includea magnetic recording apparatus, an optical disk, a magneto-optical disk,and/or a semiconductor memory (for example, RAM, ROM, etc.). Examples ofthe magnetic recording apparatus include a hard disk device (HDD), aflexible disk (FD), and a magnetic tape (MT). Examples of the opticaldisk include a DVD (Digital Versatile Disc), a DVD-RAM, a CD-ROM(Compact Disc-Read Only Memory), and a CD-R (Recordable)/RW.

As described above, the methods and systems in accordance with variousexemplary embodiments can be used in conjunction with a surgicalinstrument having an end effector configured to perform multiplesurgical procedures via components that are actuated via a transmissionmechanism at the proximal end of the instrument. Further, according toan aspect of the embodiments, any combinations of the describedfeatures, functions and/or operations can be provided.

Other embodiments of the invention will be apparent to those skilled inthe art from consideration of the specification and practice of thepresent disclosure and claims herein. It is intended that thespecification and examples be considered as exemplary only, with a truescope and spirit of the invention being indicated by the followingclaims.

What is claimed is:
 1. A method of controlling a gripping force of anend effector of a surgical instrument, the method comprising: receivinga first input signal in response to grip input at a master grip inputmechanism that controls slave gripping force of the end effector; inresponse to receiving the first input signal, increasing the slavegripping force of the end effector to a first threshold level; receivinga second input signal after receiving the first input signal, whereinthe second input signal is received in response to a procedure input ata master input device, the procedure input being other than grip inputat the master grip input mechanism, the procedure input causingactuation of the surgical instrument to perform a first surgicalprocedure; and in response to receiving at least the second input signalwhile continuing to receive the first input signal, increasing the slavegripping force of the end effector from the first threshold level to asecond level higher than the first threshold level during the firstsurgical procedure.
 2. The method of claim 1, further comprising:outputting a locking signal in response to receiving the first inputsignal and the second input signal to lock one or more degrees offreedom of the surgical instrument during the first surgical procedure.3. The method of claim 1, wherein the first input signal is output whenthe grip input at the master grip input mechanism meets a squeezingforce threshold.
 4. The method of claim 3, wherein the squeezing forcethreshold is reached at 80 percent or more of a fully actuated positionof the master grip input mechanism to actuate the slave gripping force.5. The method of claim 3, wherein the master grip input mechanismcomprises a biasing transition mechanism comprising a first biasingmechanism and a second biasing mechanism, wherein the first biasingmechanism provides haptic feedback to a user to indicate squeezingagainst a first level of resistance to indicate a lower gripping force,and wherein the second biasing mechanism provides haptic feedback to auser to indicate squeezing against a second level of resistance toindicate a higher gripping force.
 6. The method of claim 5, wherein thesqueezing force threshold is reached at 80 percent or more of an amountof a fully compressed state of the second biasing mechanism.
 7. Themethod of claim 1, further comprising decreasing the slave grippingforce of the end effector from the second level.
 8. The method of claim7, wherein decreasing the slave gripping force occurs in response to arelease of the master grip input mechanism exceeding a releasingthreshold.
 9. The method of claim 8, wherein the releasing threshold is20 percent or more of an amount the master grip input mechanism has beenreleased after the grip input causes a compressing of the master gripinput mechanism to actuate the slave gripping force.
 10. The method ofclaim 8, wherein the master grip input mechanism comprises a biasingtransition mechanism comprising a first biasing mechanism and a secondbiasing mechanism, wherein the first biasing mechanism provides hapticfeedback to a user to indicate squeezing against a first level ofresistance to indicate a lower gripping force, and wherein the secondbiasing mechanism provides haptic feedback to a user to indicatesqueezing against a second level of resistance to indicate a highergripping force.
 11. The method of claim 10, wherein the releasingthreshold is 20 percent or more of an amount the second biasingmechanism is released from a fully compressed state.
 12. The method ofclaim 8, wherein decreasing the slave gripping force comprisesdecreasing the slave gripping force from the second level to a zerogripping force level when the releasing threshold is exceeded.
 13. Themethod of claim 7, wherein decreasing the slave gripping force occurs inresponse to one or more of an indication that the first surgicalprocedure is to end or an indication that the first surgical procedurehas ended.
 14. The method of claim 13, wherein decreasing the slavegripping force comprises decreasing the slave gripping force from thesecond level to the first level.
 15. The method of claim 13, whereincessation of the second input signal indicates that the first surgicalprocedure is to end.
 16. The method of claim 13, wherein the indicationthat the first surgical procedure has ended is determined from one ormore of information detected from tissue, a position of an element ofthe end effector, and an elapsed time from initiation of the firstsurgical procedure.
 17. The method of claim 1, wherein receiving thesecond input signal comprises receiving an arming input signal inresponse to an arming input to arm the surgical instrument to perform acutting procedure.
 18. The method of claim 17, further comprisingreceiving a cutting input signal after the arming input signal, thecutting input signal indicating that the cutting procedure is to begin.19. The method of claim 18, further comprising decreasing the slavegripping force of the end effector between the arming of the surgicalinstrument and the cutting procedure.
 20. The method of claim 18,wherein the second level of the slave gripping force is maintainedbetween the arming of the surgical instrument and the cutting procedure.21. The method of claim 1, further comprising receiving a third inputsignal, subsequent to completion of the first surgical procedure and inresponse to a subsequent procedure input at the master input device toactuate the surgical instrument to perform a subsequent surgicalprocedure, wherein the second level of the slave gripping force ismaintained between the first surgical procedure and the subsequentsurgical procedure.
 22. The method of claim 1, further comprising:receiving a third input signal, subsequent to completion of the firstsurgical procedure and in response to a subsequent procedure input atthe master input device to actuate the surgical instrument to perform asubsequent surgical procedure; and decreasing the slave gripping forceof the end effector between the first surgical procedure and thesubsequent surgical procedure.
 23. A surgical system, comprising: amaster grip input mechanism; a surgical instrument comprising an endeffector, wherein the end effector is configured to apply slave grippingforce in response to grip input at the master grip input mechanism; anda controller configured to: receive a first input signal in response togrip input at the master grip input mechanism; in response to receivingthe first input signal, output a first actuation signal to increaseslave gripping force of the end effector to a first threshold level;receive a second input signal after receiving the first input signal,wherein the second input signal is received in response to a procedureinput at a master input device, the procedure input being other thangrip input at the master grip input mechanism and causing actuation ofthe surgical instrument to perform a first surgical procedure; andoutput a second actuation signal, in response to receiving at least thesecond input signal while continuing to receive the first input signal,the second actuation signal causing the slave gripping force of the endeffector to increase from the first threshold level to a second levelhigher than the first threshold level during the first surgicalprocedure.
 24. The surgical system of claim 23, wherein the controlleris further configured to output a locking signal, in response toreceiving at least the second input signal, the locking signal causingone or more degrees of freedom of the surgical instrument to be lockedduring the first surgical procedure.
 25. The surgical system of claim23, wherein the controller is further configured to output a thirdactuation signal, the third actuation signal causing the slave grippingforce of the end effector to be decreased.
 26. The surgical system ofclaim 25, wherein the controller is configured to output the thirdactuation signal in response to a release of the master grip inputmechanism.
 27. The surgical system of claim 23, wherein the second inputsignal is an arming input signal output in response to an arming inputto arm the surgical instrument to perform a cutting procedure with theend effector.
 28. The surgical system of claim 23, wherein thecontroller is further configured to receive a third input signal,subsequent to completion of the first surgical procedure and in responseto a subsequent procedure input at the master input device or anothermaster input device, to actuate the surgical instrument to perform asubsequent surgical procedure, wherein the gripping force is maintainedat the second level between the first surgical procedure and thesubsequent surgical procedure.
 29. The system of claim 23, wherein thecontroller is further configured to: receive a third input signal,subsequent to completion of the first surgical procedure and in responseto a subsequent procedure input at the master input device or anothermaster input device, to actuate the surgical instrument to perform asubsequent surgical procedure; and output a third actuation signalcausing the slave gripping force of the end effector to decrease betweenthe first surgical procedure and the subsequent surgical procedure.